Conclusion:
This is the first report of germline mutations in presumed S-PCT patients, indicating that these manifesting patients either had de novo mutations or F-PCT that masqueraded as S-PCT due to the low penetrance of the germline mutations. Therefore, biochemically confirmed S-PCT patients should be screened by mutation analysis. In addition, no sequence variants or SNPs were identified in the URO-D gene that predisposed patients to S-PCT.